"The relatively low productivity trend could remain constant until something changes."

Will our children really not know economic growth? This is the title of a balanced review by Larry Summers of economist Robert Gordon’s – pessimistic – expectations of US growth in The Rise and Fall of American Growth: The US Standard of Living since the Civil War.

The easy conclusion would be to assume the economists do not know and cannot guess, given Gordon was among a host of economists a decade earlier predicting productivity would average 2.2% to 2.8%…